How did the ancient computers in 60's era nukes aim to multiple targets?

[Stranger_On_A_Train]

@Tuckerfan

I know that the computers used on the LEM, were really little more than automated sequencers (and stored data on a wire), and that if you threw too much at them, or if the data was too far out of line with what it was told to expect, they were utterly useless. I’d imagine that the technology used for guidance on the missile systems was pretty similar.

This isn’t quite true. The LM used the same type of computer–theApollo Guidance Computer, an early version of what would become the IBM AP-101–as the core of the Primary Guidance, Navigation and Control System (PGNS or ‘pings’). This was, in fact, an early integrated circuit computer programmed in HAL/S. (Trivia: the error code used to indicate null or bad data coming from the IMU–code 00404–is the basis for the “404: Page Not Found” error code in HTTP.) The LM also had a backup computer, the TRW-designed Abort Guidence System, used for ascent if PGNS failed. The Autonetics D-37C used in Minuteman II was an entirely different system, as was the D-37D and Honeywell HDC-701 used on Minuteman III. Minuteman I and II used rotating disc storage, not because it was more robust, but because it was faster than ferrite core memory storage of the day. MM-III went to a solid-state storage system.

@Tuckerfan

And don’t underestimate the power of tube based computing for years after the US military switched to solid state electronics, the USSR kept on using tubes. There’s an account of US engineers pouring over a captured Soviet fighter and laughing that it still had tubes, until one of the engineers pointed out that the plane could survive an EMP with no problems, while a US fighter would have had it’s electronics fried.

That would be the vaunted MiG-25 ‘Foxbat’. The main purpose in using vacuum tubes in avionics and ECM systems was not that it was resistant to EMP but because they were easier to test and replace in rough field conditions the MiG-25 was likely to operate in, and because Soviet manufacturing technology had substantial quality control problems in producing reliable IC circuits.

@Triskadecamus

The target circle of the ICBM of the sixties, and the seventies was a Kilometer or more in radius. Hence, the drive for bigger and bigger warheads. The size of the explosion was what made the weapon feasible at all. Missing by half a mile was probably not enough to leave the target safe.

Part of the drive for larger warheads was greater coverage to accomodate less accurate targeting, but in large measure it was to strike on hardened missile silos; whereas previous systems were “soft” (above ground) or “semi-hardened” (below ground but elevated and fueled before launch) the newest generation of ICBMs were stored essentially ready to launch in hardened underground silos, making a near-miss of a missile facility with a smaller weapon useless. With the advent of more precise targeting and MIRV capability (which led to a new and even more disturbing proliferation of weapons) and a reduced likelyhood of being able to launch a disarming strike due to increased early warning capability by both parties, large warheads were found to be inefficient and marginally useful for most deterrent purposes, especially under the (Mutually) Assured Destruction philosophy of American strategists. (The Soviets never adopted the tenets of Assured Destruction as a whole and thus maintained a larger arsenal of multi-megaton weapons while also fielding massive boosters with comparatively huge throw weight, eventually frightening the US into fielding the LGM-118A ‘Peacekeeper’ in response.)

MIRVs also had the side effect of making terminal-phase ABM against a strategic full-on attack essentially useless. When the enemy was targeting two or three massive RVs toward a known target it was feasible (if just but) to effect an ABM interceptor system with a reasonable (although hardly assured) probability of intercept. When the enemy can afford to pitch a dozen or more RVs at a target area, the probability that at least one or more will penetrate is almost certain versus any realistic probability of intercept.

Stranger

[Rysto]

@Pochacco

The Minuteman II, fielded in the mid-60’s, was one of the first practical applications of integrated circuits.

My bad, I misremembered. For some reason I thought that ICs were introduced in 1972; I think that I was off by a decade.

[R.P.McMurphy]

They didn’t use any Microsoft products.

[mwbrooks]

@Rysto

My bad, I misremembered. For some reason I thought that ICs were introduced in 1972; I think that I was off by a decade.

That’s when the first microcomputer (Intel’s 4004) was introduced, or, rather, at the end of 1971.

[mks57]

Someone once told me that a substantial amount of resources were spent on the development of star sensors, which were small devices that could be used to obtain accurate mid-flight navigation fixes by using known stars as position references.

[astro]

@mks57

Someone once told me that a substantial amount of resources were spent on the development of star sensors, which were small devices that could be used to obtain accurate mid-flight navigation fixes by using known stars as position references.

From Danlan’s guidance computer link

Celestial guidance
Celestial guidance was first used in the American Poseidon missile and uses star positioning to fine-tune the accuracy of the inertial guidance system after launch. As the accuracy of a ballistic missile is dependent upon the guidance system knowing the exact position of the rocket at any given moment during its boost phase, the fact that stars are a fixed reference point from which to calculate that position makes this a potentially very effective means of improving accuracy. In the Polaris system this was achieved by a single camera that was trained to spot just one star in its expected position (it is believed that the missiles from Soviet submarines would track two separate stars to achieve this), if it was not quite aligned to where it should be then this would indicate that the inertial system was not precisely on target and a correction would be made. Apparently this system is sufficiently sensitive to detect stars in daylight.[citation needed